FIS1 and neoplasm: The fusion proteins, including mitofusins (MFN1, MFN2) and optic atrophy (OPA1), as well as fission proteins, including mitochondrial fission 1 (FIS1) and dynamin-1-like (DRP1), play an important role in the dynamic changes of the mitochondria19, and although incompletely understood, mitochondrial morphological changes appear to be involved in several activities critical to cell health and tumor cells20.